package com.hankcs.lucene;

import org.apache.lucene.util.ArrayUtil;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * 抄袭lucene的英文处理
 * Stemmer, implementing the Porter Stemming Algorithm
 * <p/>
 * The Stemmer class transforms a word into its root form. The input word can be
 * provided a character at time (by calling add()), or at once by calling one of
 * the various stem(something) methods.
 */

public class PorterStemmer
{
    private char[] b;
    private int i, /* offset into b */
            j, k, k0;
    private boolean dirty = false;
    private static final int INITIAL_SIZE = 50;

    public PorterStemmer()
    {
        b = new char[INITIAL_SIZE];
        i = 0;
    }

    /**
     * reset() resets the stemmer so it can stem another word. If you invoke the
     * stemmer by calling add(char) and then stem(), you must call reset()
     * before starting another word.
     */
    public void reset()
    {
        i = 0;
        dirty = false;
    }

    /**
     * Add a character to the word being stemmed. When you are finished adding
     * characters, you can call stem(void) to process the word.
     */
    public void add(char ch)
    {
        if (b.length <= i)
        {
            b = ArrayUtil.grow(b, i + 1);
        }
        b[i++] = ch;
    }

    /**
     * After a word has been stemmed, it can be retrieved by toString(), or a
     * reference to the internal buffer can be retrieved by getResultBuffer and
     * getResultLength (which is generally more efficient.)
     */
    @Override
    public String toString()
    {
        return new String(b, 0, i);
    }

    /**
     * Returns the length of the word resulting from the stemming process.
     */
    public int getResultLength()
    {
        return i;
    }

    /**
     * Returns a reference to a character buffer containing the results of the
     * stemming process. You also need to consult getResultLength() to determine
     * the length of the result.
     */
    public char[] getResultBuffer()
    {
        return b;
    }

	/* cons(i) is true <=> b[i] is a consonant. */

    private final boolean cons(int i)
    {
        switch (b[i])
        {
            case 'a':
            case 'e':
            case 'i':
            case 'o':
            case 'u':
                return false;
            case 'y':
                return (i == k0) ? true : !cons(i - 1);
            default:
                return true;
        }
    }

	/*
     * m() measures the number of consonant sequences between k0 and j. if c is
	 * a consonant sequence and v a vowel sequence, and <..> indicates arbitrary
	 * presence,
	 * 
	 * <c><v> gives 0 <c>vc<v> gives 1 <c>vcvc<v> gives 2 <c>vcvcvc<v> gives 3
	 * ....
	 */

    private final int m()
    {
        int n = 0;
        int i = k0;
        while (true)
        {
            if (i > j)
                return n;
            if (!cons(i))
                break;
            i++;
        }
        i++;
        while (true)
        {
            while (true)
            {
                if (i > j)
                    return n;
                if (cons(i))
                    break;
                i++;
            }
            i++;
            n++;
            while (true)
            {
                if (i > j)
                    return n;
                if (!cons(i))
                    break;
                i++;
            }
            i++;
        }
    }

	/* vowelinstem() is true <=> k0,...j contains a vowel */

    private final boolean vowelinstem()
    {
        int i;
        for (i = k0; i <= j; i++)
            if (!cons(i))
                return true;
        return false;
    }

	/* doublec(j) is true <=> j,(j-1) contain a double consonant. */

    private final boolean doublec(int j)
    {
        if (j < k0 + 1)
            return false;
        if (b[j] != b[j - 1])
            return false;
        return cons(j);
    }

	/*
	 * cvc(i) is true <=> i-2,i-1,i has the form consonant - vowel - consonant
	 * and also if the second c is not w,x or y. this is used when trying to
	 * restore an e at the end of a short word. e.g.
	 * 
	 * cav(e), lov(e), hop(e), crim(e), but snow, box, tray.
	 */

    private final boolean cvc(int i)
    {
        if (i < k0 + 2 || !cons(i) || cons(i - 1) || !cons(i - 2))
            return false;
        else
        {
            int ch = b[i];
            if (ch == 'w' || ch == 'x' || ch == 'y')
                return false;
        }
        return true;
    }

    private final boolean ends(String s)
    {
        int l = s.length();
        int o = k - l + 1;
        if (o < k0)
            return false;
        for (int i = 0; i < l; i++)
            if (b[o + i] != s.charAt(i))
                return false;
        j = k - l;
        return true;
    }

	/*
	 * setto(s) sets (j+1),...k to the characters in the string s, readjusting
	 * k.
	 */

    void setto(String s)
    {
        int l = s.length();
        int o = j + 1;
        for (int i = 0; i < l; i++)
            b[o + i] = s.charAt(i);
        k = j + l;
        dirty = true;
    }

	/* r(s) is used further down. */

    void r(String s)
    {
        if (m() > 0)
            setto(s);
    }

	/*
	 * step1() gets rid of plurals and -ed or -ing. e.g.
	 * 
	 * caresses -> caress ponies -> poni ties -> ti caress -> caress cats -> cat
	 * 
	 * feed -> feed agreed -> agree disabled -> disable
	 * 
	 * matting -> mat mating -> mate meeting -> meet milling -> mill messing ->
	 * mess
	 * 
	 * meetings -> meet
	 */

    private final void step1()
    {
        if (b[k] == 's')
        {
            if (ends("sses"))
                k -= 2;
            else if (ends("ies"))
                setto("i");
            else if (b[k - 1] != 's')
                k--;
        }
        if (ends("eed"))
        {
            if (m() > 0)
                k--;
        }
        else if ((ends("ed") || ends("ing")) && vowelinstem())
        {
            k = j;
            if (ends("at"))
                setto("ate");
            else if (ends("bl"))
                setto("ble");
            else if (ends("iz"))
                setto("ize");
            else if (doublec(k))
            {
                int ch = b[k--];
                if (ch == 'l' || ch == 's' || ch == 'z')
                    k++;
            }
            else if (m() == 1 && cvc(k))
                setto("e");
        }
    }

	/* step2() turns terminal y to i when there is another vowel in the stem. */

    private final void step2()
    {
        if (ends("y") && vowelinstem())
        {
            b[k] = 'i';
            dirty = true;
        }
    }

	/*
	 * step3() maps double suffices to single ones. so -ization ( = -ize plus
	 * -ation) maps to -ize etc. note that the string before the suffix must
	 * give m() > 0.
	 */

    private final void step3()
    {
        if (k == k0)
            return; /* For Bug 1 */
        switch (b[k - 1])
        {
            case 'a':
                if (ends("ational"))
                {
                    r("ate");
                    break;
                }
                if (ends("tional"))
                {
                    r("tion");
                    break;
                }
                break;
            case 'c':
                if (ends("enci"))
                {
                    r("ence");
                    break;
                }
                if (ends("anci"))
                {
                    r("ance");
                    break;
                }
                break;
            case 'e':
                if (ends("izer"))
                {
                    r("ize");
                    break;
                }
                break;
            case 'l':
                if (ends("bli"))
                {
                    r("ble");
                    break;
                }
                if (ends("alli"))
                {
                    r("al");
                    break;
                }
                if (ends("entli"))
                {
                    r("ent");
                    break;
                }
                if (ends("eli"))
                {
                    r("e");
                    break;
                }
                if (ends("ousli"))
                {
                    r("ous");
                    break;
                }
                break;
            case 'o':
                if (ends("ization"))
                {
                    r("ize");
                    break;
                }
                if (ends("ation"))
                {
                    r("ate");
                    break;
                }
                if (ends("ator"))
                {
                    r("ate");
                    break;
                }
                break;
            case 's':
                if (ends("alism"))
                {
                    r("al");
                    break;
                }
                if (ends("iveness"))
                {
                    r("ive");
                    break;
                }
                if (ends("fulness"))
                {
                    r("ful");
                    break;
                }
                if (ends("ousness"))
                {
                    r("ous");
                    break;
                }
                break;
            case 't':
                if (ends("aliti"))
                {
                    r("al");
                    break;
                }
                if (ends("iviti"))
                {
                    r("ive");
                    break;
                }
                if (ends("biliti"))
                {
                    r("ble");
                    break;
                }
                break;
            case 'g':
                if (ends("logi"))
                {
                    r("log");
                    break;
                }
        }
    }

	/* step4() deals with -ic-, -full, -ness etc. similar strategy to step3. */

    private final void step4()
    {
        switch (b[k])
        {
            case 'e':
                if (ends("icate"))
                {
                    r("ic");
                    break;
                }
                if (ends("ative"))
                {
                    r("");
                    break;
                }
                if (ends("alize"))
                {
                    r("al");
                    break;
                }
                break;
            case 'i':
                if (ends("iciti"))
                {
                    r("ic");
                    break;
                }
                break;
            case 'l':
                if (ends("ical"))
                {
                    r("ic");
                    break;
                }
                if (ends("ful"))
                {
                    r("");
                    break;
                }
                break;
            case 's':
                if (ends("ness"))
                {
                    r("");
                    break;
                }
                break;
        }
    }

	/* step5() takes off -ant, -ence etc., in context <c>vcvc<v>. */

    private final void step5()
    {
        if (k == k0)
            return; /* for Bug 1 */
        switch (b[k - 1])
        {
            case 'a':
                if (ends("al"))
                    break;
                return;
            case 'c':
                if (ends("ance"))
                    break;
                if (ends("ence"))
                    break;
                return;
            case 'e':
                if (ends("er"))
                    break;
                return;
            case 'i':
                if (ends("ic"))
                    break;
                return;
            case 'l':
                if (ends("able"))
                    break;
                if (ends("ible"))
                    break;
                return;
            case 'n':
                if (ends("ant"))
                    break;
                if (ends("ement"))
                    break;
                if (ends("ment"))
                    break;
			/* element etc. not stripped before the m */
                if (ends("ent"))
                    break;
                return;
            case 'o':
                if (ends("ion") && j >= 0 && (b[j] == 's' || b[j] == 't'))
                    break;
			/* j >= 0 fixes Bug 2 */
                if (ends("ou"))
                    break;
                return;
			/* takes care of -ous */
            case 's':
                if (ends("ism"))
                    break;
                return;
            case 't':
                if (ends("ate"))
                    break;
                if (ends("iti"))
                    break;
                return;
            case 'u':
                if (ends("ous"))
                    break;
                return;
            case 'v':
                if (ends("ive"))
                    break;
                return;
            case 'z':
                if (ends("ize"))
                    break;
                return;
            default:
                return;
        }
        if (m() > 1)
            k = j;
    }

	/* step6() removes a final -e if m() > 1. */

    private final void step6()
    {
        j = k;
        if (b[k] == 'e')
        {
            int a = m();
            if (a > 1 || a == 1 && !cvc(k - 1))
                k--;
        }
        if (b[k] == 'l' && doublec(k) && m() > 1)
            k--;
    }

    /**
     * Stem a word provided as a String. Returns the result as a String.
     */
    public String stem(String s)
    {
        if (stem(s.toCharArray(), s.length()))
            return toString();
        else
            return s;
    }

    /**
     * Stem a word contained in a char[]. Returns true if the stemming process
     * resulted in a word different from the input. You can retrieve the result
     * with getResultLength()/getResultBuffer() or toString().
     */
    public boolean stem(char[] word)
    {
        return stem(word, word.length);
    }

    /**
     * Stem a word contained in a portion of a char[] array. Returns true if the
     * stemming process resulted in a word different from the input. You can
     * retrieve the result with getResultLength()/getResultBuffer() or
     * toString().
     */
    public boolean stem(char[] wordBuffer, int offset, int wordLen)
    {
        reset();
        if (b.length < wordLen)
        {
            b = new char[ArrayUtil.oversize(wordLen, Character.BYTES)];
        }
        System.arraycopy(wordBuffer, offset, b, 0, wordLen);
        i = wordLen;
        return stem(0);
    }

    /**
     * Stem a word contained in a leading portion of a char[] array. Returns
     * true if the stemming process resulted in a word different from the input.
     * You can retrieve the result with getResultLength()/getResultBuffer() or
     * toString().
     */
    public boolean stem(char[] word, int wordLen)
    {
        return stem(word, 0, wordLen);
    }

    /**
     * Stem the word placed into the Stemmer buffer through calls to add().
     * Returns true if the stemming process resulted in a word different from
     * the input. You can retrieve the result with
     * getResultLength()/getResultBuffer() or toString().
     */
    public boolean stem()
    {
        return stem(0);
    }

    public boolean stem(int i0)
    {
        k = i - 1;
        k0 = i0;
        if (k > k0 + 1)
        {
            step1();
            step2();
            step3();
            step4();
            step5();
            step6();
        }
        // Also, a word is considered dirty if we lopped off letters
        // Thanks to Ifigenia Vairelles for pointing this out.
        if (i != k + 1)
            dirty = true;
        i = k + 1;
        return dirty;
    }

    /**
     * Test program for demonstrating the Stemmer. It reads a file and stems
     * each word, writing the result to standard out. Usage: Stemmer file-name
     */
    public static void main(String[] args)
    {
        PorterStemmer s = new PorterStemmer();

        for (int i = 0; i < args.length; i++)
        {
            try
            {
                InputStream in = new FileInputStream(args[i]);
                byte[] buffer = new byte[1024];
                int bufferLen, offset, ch;

                bufferLen = in.read(buffer);
                offset = 0;
                s.reset();

                while (true)
                {
                    if (offset < bufferLen)
                        ch = buffer[offset++];
                    else
                    {
                        bufferLen = in.read(buffer);
                        offset = 0;
                        if (bufferLen < 0)
                            ch = -1;
                        else
                            ch = buffer[offset++];
                    }

                    if (Character.isLetter((char) ch))
                    {
                        s.add(Character.toLowerCase((char) ch));
                    }
                    else
                    {
                        s.stem();
                        System.out.print(s.toString());
                        s.reset();
                        if (ch < 0)
                            break;
                        else
                        {
                            System.out.print((char) ch);
                        }
                    }
                }

                in.close();
            }
            catch (IOException e)
            {
                System.out.println("error reading " + args[i]);
            }
        }
    }

}
